Having studied at all three theaters:
Armando is the best teacher. He's like not human. But there are plenty of other great ones.
I found myself in Pat Shay's class at the PIT. Pat is one of those people I believe in.
I made major progress studying with Billy Merritt at UCB also.
And Louis Kornfeld at Magnet opened me up to a school of improv that valued all the traditional elements of theatre and didn't rely on exposition, whackiness or GAME (I despise game with a passion).
I wouldn't call them Gods like the names above, but Alex Marino and Peter McNerney both opened me up to looking at improv in new and exciting ways. I just started with James Eason, but I get the same feeling from him.
Here are the ones who were also great:
PIT: Kurt Braunohler, Matt Donnelly, Rebekka Johnson
UCB: Kevin Hines, Shannon O'Neill (sp?, sorry Shannon), Neil Casey, Gavin Speiller
MAG: Tara Copeland (everyone should take a class with her), Rachel Hamilton, Blaine Swen
I didn't have a great time in Joe Wengert's class, largely due to philosophical differences. I like Joe a lot personally and he was very accommodating of the fact that we had differing dispositions, once he realized, which I think takes a lot of fortitude. I admire him for it.
I had a bad experience with Ali Faranahkian. He actually taught me some useful stuff, but some of what he has to say, I feel, is destructive. I also found him difficult to get along with on a personal level, as I think he found me.
And my worst experience was with Anthony King. I'm sure that'll prevent me from ever getting on a harold team, but I don't care. I felt Anthony was solipsistic about performing and closed-minded about what improv was, could only suggest we think the way he did and made the moves he did. Several of the points he made about improv, which I agree with in the context of improv, he would use to describe "comedy." I strongly disagreed with several of them. I have avoided UCB somewhat as a result since then, which is really a shame. His class and philosophy just left such a bitter taste in my mouth. I feel like I made backwards progress in it.
I've also had Gil Ozeri as a substitute and Brandon Gardner as a coach. Both have GREAT things to say that are unique to them and I high recommend both of them. Both are also great guys.
I don't mean to step on any toes. I've had mostly good experiences at all three theaters. I personally think Magnet is the bees knees, particularly if you want to get into the wider world of narrative film and television, but I learned valuable things at the other two as well.
I hope no one will hold it against me for honestly stating my preferences and experiences. I don't want to step on anyone's toes, but there's a point where honest information must be conveyed.